1. Field of the Invention
This invention relates to computer systems and, more particularly, to methods and apparatus for changing the size of graphic data for presentation on an television output display.
2. History of the Prior Art
There have been various attempts to combine video data (data used to display television) and graphics data (data used to provide a computer display) for presentation on an output display. Most of these attempts have been directed to providing television programs in a window on a computer screen.
Only a few attempts have been made to provide computer graphics output on a television output display. Because the format of the two sources is so different, it has been the practice to import the video signals into computer frame buffer memory, change the various signals to the format utilized on the chosen output display, combine the signals, and transfer the data to the output display. In general, this has slowed the presentation of all data on the output display because of the large amount of bus time occupied by the video data.
Recently a system utilizing new methods and apparatus for combining video and computer graphics data has been devised. The system is capable of producing displays which accurately present and are capable of differentiating each of the individual streams for presentation on either an analog or a digital output display. The system is especially designed to provide data streams for digital information displays which appear to be the choice for the future of both television and computers. Such a system is described in detailed in U.S. patent application Ser. No. 09/276,878, entitled Method And Apparatus For Combining Video And Graphics, Jhi-Chung Kuo et al, filed Mar. 26, 1999, and assigned to the assignee of the present invention.
A major use of the new system is to present on a television output display graphical information originating on the internet and especially on the World Wide Web. One of the problems encountered in attempting to display graphical data originating on the web is that most such data is originally generated by a computer system and is intended to be displayed on a computer output display. A computer display typically offers a much more detailed picture than a television display, and pictures which are quite clear and readable on a computer display are often undecipherable on a television output display. This is often because the fonts utilized are simply too small for display by a television display.
In order to overcome this problem, the prior art has typically utilized software running on the processor which is obtaining the graphical data from the internet to enlarge the computer-generated image sufficiently for display on a television screen. A problem with this approach is that processors utilized to access the web are often those included in xe2x80x9cset top boxes.xe2x80x9d Such processors are typically less powerful that those used by a typical computer. Using a slow processor to access computer graphics data in a frame buffer, to enlarge that data using software executing on the processor, and to rewrite the enlarged data to the frame buffer for presentation on the television output display often produces an unsatisfactory result.
To obviate this difficulty, some web sites produce one set of output signals for computer displays and another set of output signals for television displays. Producing two sets of data is quite expensive and, consequently, is not practiced by the majority of web sites which it might be desirable to display on a television screen.
Another difficulty encountered is that graphical display data originating on the web or from some other computer-generated source is usually of a shape different from that designed for a television display. Many images have been individually created by graphics artists for computer use. In order to display such images on television, an artist must often prepare separate images for a television display at additional expense.
An additional problem with material generated originally for display by a computer is that text is often presented in a color index format. In such a format, index values for pixels utilize a lookup table to provide color values for presentation on a computer display. Index values themselves cannot be enlarged for presentation on a television display because they bear no relation to the color values they represent except through a lookup table. The attempt to enlarge index values provides representations which are often quite unattractive when presented on a television display.
It is desirable to provide means by which computer graphics images may be readily utilized for display on a television output display at an acceptable output rate without excessive cost.
The present invention is realized by a circuit utilized to convert a selected portion of graphics data generated for a computer display into video data for presentation on a selected portion of a television display comprising a first data path for transferring graphics data from a source of graphics data to a television display without changing the size of the data, a second data path for transferring graphics data from a the source of graphics data to a television display while selectably changing the size of the data, the second data path including circuitry for selecting a portion of the television display on which to present the selected data transferred by the second data path, and zooming circuitry for enlarging data transferred by the second data path to fill the selected portion of the television display.
This and other objects and features of the invention will be better understood by reference to the detailed description which follows taken together with the drawings in which like elements are referred to by like designations throughout the several views.